Fuel cells capable of power generation at a high efficiency even with a small size is being progressively developed as a key component of a power generation system for a distributed energy supply source. A supply system of hydrogen gas, which is a fuel necessary for power generation, is not sufficiently provided as a general infrastructure. Therefore, a hydrogen generation apparatus including a reformer for generating hydrogen-containing gas using a raw material (hydrocarbon-based gas) supplied from an existing fossil raw material infrastructure such as, for example, city gas, propane gas or the like (the hydrogen generation apparatus is also referred to as the “fuel reforming apparatus”) is installed together with the fuel cell.
Hydrocarbon-based gas such as city gas, propane gas or the like which is supplied from an existing infrastructure usually contains an odorant, including an odorizer component such as a sulfur compound, a nitrogen-containing compound or the like, generally at a volume concentration of about several ppm's. Representative sulfur compounds used as an odorizer component include sulfides such as dimethylsulfide (CH3SCH3) and the like, mercaptans such as tertiary butylmercaptan ((CH3)3CSH) and the like, and thiophenes such as tetrahydrothiophene and the like. Nitrogen-containing compounds used as an odorizer component include, for example, pyrazines such as 2-alkoxy-3-butylpyrazine and the like, nitrogen-based lower fatty acids, pyridines, and pyrimidines.
Such an odorant is added in order to detect a gas leak from a pipe or the like of the infrastructure line. However, especially an odorizer component contained in the odorant such as a sulfur compound may poison a catalyst used in the reformer. Accordingly, in order to suppress the poisoning influence of sulfur on the catalyst, the odorizer component needs to be removed from the raw material such as city gas, propane gas or the like before the raw material is supplied to the reformer.
Patent Documents Nos. 1 and 2 propose that in order to remove a sulfur compound from a raw material, the sulfur compound in the raw material is adsorbed by an adsorbing desulfurization section using an zeolite-based adsorbing agent.
With the adsorbing desulfurization section using an zeolite-based adsorbing agent, the adsorbing capacity on a sulfur compound is small. In order to sufficiently suppress the poisoning influence of sulfur on the catalyst used in the reformer, the adsorbing desulfurization section needs to be exchanged every certain time period. For example, Patent Document No. 3 proposes using an adsorbing agent having an indicator function, by which the time to exchange the adsorbing agent can be easily determined. Patent Document No. 4 filed by the present Applicant describes applying an adsorbing desulfurization section detachable from a power generation system using a fuel cell (fuel cell power generation system) and determining the time to exchange the adsorbing desulfurization section based on an accumulated amount of the raw material gas which has passed the section. Patent Document No. 5 proposes a method of networking a plurality of fuel cell power generation systems installed at houses and facilities to determine the time to exchange the adsorbing desulfurization section.
Instead of exchanging the adsorbing desulfurization section, the adsorbing agent contained in the adsorbing desulfurization section may be regenerated. A method for reproducing the adsorbing agent is proposed in, for example, Patent Documents Nos. 6 and 7.    Patent Document No. 1: Japanese Laid-Open Patent Publication No. 10-237473    Patent Document No. 2: Japanese Laid-Open Patent Publication No. 2004-228016    Patent Document No. 3: Japanese Laid-Open Patent Publication No. 2002-358992    Patent Document No. 4: Japanese Laid-Open Patent Publication No. 2006-8459    Patent Document No. 5: Japanese Laid-Open Patent Publication No. 2006-278120    Patent Document No. 6: Japanese Laid-Open Patent Publication No. 11-309329    Patent Document No. 7: Japanese Laid-Open Patent Publication No. 2007-123269